1. Field of the Invention
This invention relates generally to electric circuit breakers and more particularly to the indication of the status of a circuit breaker and the remote control of a circuit breaker.
2. Description of the Related Art
Circuit breakers are commonly used for temporary interruption of electrical power to electrically powered devices. Various circuit breaker mechanisms have evolved and have been perfected over time on the basis of application-specific factors such as current capacity, response time, and the type of reset (manual or remote) function desired of the breaker.
One type of circuit breaker mechanism employs a thermo-magnetic tripping device to trip a latch in response to a specific range of over-current conditions. In another type of circuit breaker, referred to as a double-break circuit breaker, two sets of current breaking contacts are included to accommodate a higher level of over-current conditions than can be handled by one set of contacts. U.S. Pat. No. 5,430,419 describes a typical mechanical and electrical assembly that is utilized in circuit breakers according to the present invention and is incorporated herein by reference in its entirety.
A circuit breaker has typically three possible statuses: off, where the contacts are open; on, where the contacts are closed for completing a circuit path; and tripped, where the contacts are open because of an abnormal condition. It is desirable to monitor and control a circuit breaker's status from a remote location, such as in a control center. Systems are known, such as disclosed in U.S. Pat. No. 4,794,356, which provide in the form of a modular accessory a position-indicating switch coupled directly to the movement of an electrical circuit breaker contacter. The systems provide sensing conditions indicative of the contact condition of the circuit breaker and can indicate whether the contacts have become fused together.
U.S. Pat. No. 4,794,356 describes a combined trip actuator mechanism and accessory unit for articulating the circuit breaker operating mechanism and interfacing with the accessory unit for remote trip as well as trip indication function. U.S. Pat. Nos. 4,831,221 and 4,912,439 describe auxiliary switch accessories used within industrial-grade circuit breakers. The auxiliary switch accessories interact with the circuit breaker operating mechanism to provide remote indication of the condition of the circuit breaker contacts. U.S. Pat. No. 4,864,263 describes a crossbar unit that carries the movable contact arm and provides an accurate indication as to the actual condition of the contacts. In some instances the auxiliary switch accessory unit operates directly off the circuit breaker operating mechanism crossbar unit to provide an indication of the status of the circuit breaker.
U.S. Pat. No. 5,003,139 describes a circuit breaker housing modified to provide an access passage exposing a portion of the circuit breaker blade mechanism to external access and a bolt-on accessory module containing a rotor coupled to a movable coupling member configured to extend through the circuit breaker passage to engage a portion of the blade mechanism. A member carried with the blade mechanism mounted on a trip arm carried with the blade extends toward the passage to engage with the coupling member. A sensing switch is engaged by a camming surface on the rotor so that the rotor will be moved responsively to tripping and resetting of the circuit breaker blade to indicate the true position of the circuit breaker contacts. Rotation of the rotor will trip the circuit breaker when the circuit breaker is in the reset position. A solenoid is provided to engagingly rotate the rotor in the tripping direction. A single coupling element senses the state of the circuit breaker and provides means for remotely tripping it.
In general, the present invention pertains to monitoring and control of a circuit breaker from a remote location. Although devices exist for this general purpose, it is believed that a need exists for a circuit breaker accessory module capable of sensing the position of components in the circuit breaker and capable of initiating a change in the status of a circuit breaker. Such an accessory module is preferably reliable and durable and preferably incorporates advances in circuit board and switch technology when such advances improve the accessory module. Practical concerns regarding field installation are preferably addressed, and parts are preferably interchangeable so as to minimize the number of parts required.